The identity of charges generated by contact electrification on dielectrics has remained unknown for centuries and the precise determination of the charge density is also a long-standing challenge. Here, electrostatic charges on Teflon (polytetrafluoroethylene) produced by rubbing with Lucite (polymethylmethacrylate) were directly identified as electrons rather than ions by electrochemical (redox) experiments with charged Teflon used as a single electrode in solution causing various chemical reactions: pH increases; hydrogen formation; metal deposition; Fe(CN)(6)(3-) reduction; and chemiluminescence in the system of Teflon(-)/Ru(bpy)(3)(2+)/S(2)O(8)(2-) (analogous to electrogenerated chemiluminescence). Moreover, copper deposition could be amplified by depositing Pd first in a predetermined pattern, followed by electroless deposition to produce Cu lines. This process could be potentially important for microelectronic and other applications because Teflon has desirable properties including a low dielectric constant and good thermal stability. Charge density was determined using Faraday's law and the significance of electron transfer processes on charged polymers and potentially other insulators have been demonstrated.
Fluorescence imaging in vivo allows non-invasive tumor diagnostic thus permitting a direct monitoring of cancer therapies progresses. It is established herein that fluorescent gold nanoclusters are spontaneously biosynthesized by cancerous cell (i.e., HepG2, human hepatocarcinoma cell line; K562, leukemia cell line) incubated with micromolar chloroauric acid solutions, a biocompatible molecular Au(III) species. Gold nanoparticles form by Au(III) reduction inside cells cytoplasms and ultimately concentrate around their nucleoli, thus affording precise cell imaging. Importantly, this does not occur in non-cancerous cells, as evidenced with human embryo liver cells (L02) used as controls. This dichotomy is exploited for a new strategy for in vivo self-bio-imaging of tumors. Subcutaneous injections of millimolar chloroauric acid solution near xenograft tumors of the nude mouse model of hepatocellular carcinoma or chronic myeloid leukemia led to efficient biosynthesis of fluorescent gold nanoclusters without significant dissemination to the surrounding normal tissues, hence allowing specific fluorescent self-bio-marking of the tumors.
We show that pristine PMMA can spontaneously transfer electrons to species in a liquid, thereby inducing a variety of electron transfer reactions. The electrons that are transferred we call cryptoelectrons; these have a surface density of the order of 5 x 10(13) cm(-2) and are at a considerably more negative reduction potential than the PMMA bonding electrons. For example, metal ions including Ag(+), Cu(2+), and Pd(2+) were reduced and plated on a PMMA surface and Fe(CN)(6)(3-) was reduced to Fe(CN)(6)(4-). Moreover, protons were reduced when PMMA powder was dropped into a slightly acidic solution, resulting in a pH increase and hydrogen generation. Chemiluminescence was produced in a solution containing Ru(bpy)(3)(2+) and S(2)O(8)(2-) with the addition of PMMA powder. These results clearly demonstrate that there are available electrons in PMMA that can participate in redox reactions at a rather negative potential. We also show that contacting PMMA with Teflon depletes this electronic surface charge. However, the PMMA used for a redox reaction or contacted with Teflon that was depleted of the electronic surface charge could be recharged by contacting with a suitable reductant.
A molecular crystal of zinc octakis(β-decoxyethyl) porphyrin (ZnODEP) is an insulator in the dark and becomes conductive under irradiation. An externally controllable charge trapping and detrapping within ZnODEP thin films (∼1 μm) occurs when symmetrical sandwich cells of ITO/ZnODEP/ITO are irradiated under a proper bias voltage between two parallel ITO (indium−tin oxide) electrodes. The trapping and detrapping rise time is on the nanosecond time scale. Detrapping of charge stored previously in the cell could be accomplished with pulse irradiation under short-circuit conditions and gives rise to a discharge current spike. Trapped charge induced by a 10 ns laser pulse or by longer time irradiation with a conventional light source could be sensed by a voltage measurement at open circuit. No loss of stored charge was detectable at a 1 pA level for a period of 11 months under open circuit conditions in the dark. After charge trapping with 550 nm light irradiation (10 μW/cm2) under a bias of 0.5 V, the stored charge induced a voltage difference of ∼20 mV between the two ITO electrodes. This voltage difference was stable for at least 2000 h with no evidence of decay. These results suggest that ZnODEP as a thin film photoconductive insulator might serve as a memory medium for electrooptical information storage in the form of charge. Such a data storage system would be nonvolatile and rewritable. We have shown that a memory element could be subjected to write (trapping)/erase (detrapping) 1.5 billion times with a readout signal that was essentially identical with the first without any evidence of deterioration. To find attainable resolution, charge was injected with a scanning tunneling microscope tip under different bias. For a 6 V bias, charge was trapped in an element of 40 nm diameter, equivalent to a storage density of 8 × 1010 bits/cm2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.